1. Field of the Invention
The invention is related to a method and a device for controlling a thick matter pump having two conveying cylinders which are alternatingly operable by means of at least one hydraulic reversing pump and hydraulic drive cylinders driven thereby and which open into a material feed container with front face openings, and having a hydraulically actuatable pipe shunt which is disposed within the material feed container, the inlet side of which pipe shunt is adapted to be alternatingly coupled to the openings of the conveying cylinders, thereby vacating the respective other opening, and the outlet side of which pipe shunt is adapted to be connected to a conveying line, wherein a switching operation of the pipe shunt is effected upon ending a feed stroke in the conveying cylinders, wherein the drive cylinders are hydraulically connected at their one end to a respective port of the reversing pump under formation of a closed hydraulic circuit and at their other end to each other by way of an oscillating oil line, and wherein pressure oil is taken off directly from hydraulic lines which lead from the reversing pump to the drive cylinders in order to effect the switching of the pipe shunt.
2. Description of the Related Art
A method for controlling a two-cylinder thick matter pump of this kind is known (EP-B 0 446 206), wherein at the end of each pressure stroke in the conveying cylinders a switching process of the pipe shunt is effected, in which the pistons of the drive cylinders are held in their end position under the action of the pressure created by the reversing pump in the main circuit and the feed direction of the reversing pump is reversed only after finishing the switching process of the pipe shunt. When triggering the switching process of the pipe shunt, the feed quantity and/or the feed pressure of the reversing pump may be varied while keeping the feed direction constant. The switching of the pipe shunt is effected solely by means of a directional valve which is switched over while the reversing pump is still operated in the previous feed direction. This results in an undesireably hard start-up during the switching of the pipe shunt.